function get(url,params,callback,headersFn=null){
    const xhr = new XMLHttpRequest
    xhr.onreadystatechange = function(){
        if(xhr.readyState == 4)
        {
            if(xhr.status == 200)
            {
                let res = JSON.parse(xhr.responseText)
                callback(res)
            }
            else
            {
                alert("错误",xhr.status)
            }
        }  
    }
    xhr.open("get",`${url}?${params}`)
    if(headersFn) headersFn(xhr)
    xhr.send(null)
}




function post(url,params,callback,headersFn=null){
    const xhr = new XMLHttpRequest
    xhr.onreadystatechange = function(){
        if(xhr.readyState == 4)
        {
            if(xhr.status == 200)
            {
                let res = JSON.parse(xhr.responseText)
                callback(res)
            }
            else
            {
                alert("错误",xhr.status)
            }
        }  
    }
    xhr.open("post",url)
    xhr.setRequestHeader("content-type","application/x-www.form-urlencoded")
    if(headersFn) headersFn(xhr)
    xhr.send(params)
}